Radon Cluster Survey in North Dakota - 1989

During 1989, the Department began to retest those homes that
were greater than 20 pCi/l in the recently completed 1988 home
study. The home owners were asked to give names of neighbors that
might want to be tested. The neighbors were contacted and testing
began. This type of testing is referred to as a cluster survey.
The Cluster Survey indicated that a log normal distribution can
result from the subset of another log normal distribution of
radon test results. See Figure 2.

The county statistics, as found in Table 5, reflect high
arithmetic means in Stutsman and Bowman Counties and low
arithmetic means in Ward and Wells Counties.

The database contained 402 samples whose arithmetic mean was
18.8 pCi/l with a standard deviation of 22.2. There were 352 (87.6%)
samples with a radon concentration greater than 4 pCi/l. For
concentrations greater than 20 pCi/l, the 120 samples represented
29.9% of the samples.

The high percentages of samples greater than 4 or 20 pCi/l in
the basements indicates that basements should perhaps be tested
whether or not people live in the basement.

Table 5, the city/county statistics for the Cluster Survey
reveals that many cities have high averages, yet it must be
remembered that the cluster homes were all located close to a
home that was found to have a high radon concentration in the
1988 Home Study.